The present invention relates to a method of deflecting a stream of spreadable particles such as wood chips in a particle dispensing device having a rotating drivable hollow cylinder, the perforated circumference of which is normally passed through twice by the particles before they can fall in a fan-like stream, onto a support which is moved relative to said cylinder. Spreading machines having one or more hollow cylinders, are used for the forming of particle-board mats or blanks. These cylinders, which are frequently referred to as cage cylinders, have the job of defelting and uniformly distributing the particulate material. These particles are normally not identical to each other. Generally the material consists of a mixture of relatively coarse and fine particles.
Temporary deflection of the stream of particles, which is sometimes desired in a plant, poses a problem. This is so particularly when the stream of particles, which is controlled as a function of a physical variable, is to be fed periodically or sporadically during a test discharge period into a measuring device, so that the weight of the particles discharged by the spreading machine per unit of time can be monitored.
It has been customary for many years to check periodically, in the manner indicated, the uniformity of the operation of the spreading device which discharges the particles in measured quantities onto moving plates or a conveyor belt. Up to now this has been done by interrupting the formation of the mat, for instance, once an hour, for a few seconds, conducting all of part of the stream of particles to a collecting device, which is temporarily placed below the spreading device. The chips collected in this manner are fed by suitable means of conveyance, to a scale which indicates deviations from the proper weight and/or automatically readjusts the spreading device, if necessary.
This process has the disadvantage that it is necessary in each case to bring the relatively bulky collecting device into its operating position and, after the test-discharge period, to bring it back into a position in which it does not interfere with the normal spreading process. This time consuming and cumbersome manipulation not only makes operation difficult but it also increases the standstill time of the plant while the spreading is being tested.
It is also customary to arrange collecting means, for collecting the spread particles during the test discharge interval, below the following press plates on which mats are formed by the spreading of particles. These collecting means may in this connection be a conveyor belt traveling transversely to the direction of movement of the mats, said belt feeding the collected particles to the measuring device. Of course, with such a process, a test spreading is only possible if a certain minimum distance is present between the spread supports. The method accordingly cannot be used in the case of continuous spreading supports.
The object of the present invention is to provide a method for deflecting a stream of spreadable particles which is simple and rational and is adapted, for instance, to be carried out in a plant for the formation of a mat of wood particles, for the temporary deflection of the stream of chips in order to monitor the manner of operation of the plant. The above-described deficiencies should in particular be eliminated in this connection. This goal can be achieved, in accordance with the present invention, by changing the operating conditions of the cylinder, by closing the passage openings of the cylinder, by reversing its direction of rotation or by increasing its speed of rotation in such a manner that the particles rebound from the circumference of the rotating cylinder and are thrown by it in a direction which differs from the normal general direction of passage.